**3. Vertical farming: an urban farming technology**

With rapid worldwide population growth, there is scarcity of agricultural lands. It increases the demand for both more food and more land to grow food. But some entrepreneurs and farmers are beginning to find a solution to this problem, one of which can be found in the abandoned warehouses in our cities, in new buildings built on environmentally damaged lands, and even in used shipping containers from ocean transports. This solution is called vertical farming, which is an UA technology involving growing crops in controlled indoor environments, with precise light, nutrients, and temperatures.

In vertical farming, growing plants are arranged in layers that may reach several stories high. Although small-scale, residential vertical gardening (including window farms) is under practice for several years, commercial-scale vertical farms have become an important topic of discussion for the past few years in the United States. This new farming technology is growing rapidly, and entrepreneurs in many cities are taking an interest in this innovative farming system [12].

Vertical farming is gaining its importance throughout several urban cities around the world due to the beneficial role it plays in the field of agriculture. Vertical farming can reduce the transportation costs due to its adjacency to the buyer; planned production of herbs and their growing conditions can be enhanced by adjusting the temperature, humidity, lighting conditions, etc. Indoor farming in a controlled environment needs much less amount of water than outdoor farming because it involves recycling of waste water. Because of these features, vertical farming is widely implemented initially in desert and droughtstricken regions, such as some Middle Eastern countries, Africa, Israel, Japan, and the Netherlands [13].
